Boost build fails after upgrade to 1.72.0 - same target twice - c++

Question

Hello great minds of stackoverflow. My project builds Boost via a CMake ExternalProject_Add command. The b2 build command is as follows:
b2 -j${num_processors} -d 0 --layout=versioned threading=multi architecture=x86 address-model=64 link=shared --with-system --with-thread --with-date_time --with-chrono --with-atomic variant=${config_type} --prefix=${UNRELEVANT_PATH} --stagedir=${UNRELEVANT_PATH} install stage
num_processors, config_type, and UNRELEVANT_PATH are CMake variables for the number of cores on the build machine, build variant type, and paths for installation. This command works for Boost 1.62 using gcc 4.8.1 and Visual Studio 2015. We're now upgrading to Boost 1.72.0 and it is failing with this error on both compilers:
Performing configuration checks
- default address-model : 64-bit
- default architecture : x86
- lockfree boost::atomic_flag : yes
error: Name clash for '<p/my/path/to/boost/lib/cmake/boost_atomic-1.72.0>boost_atomic-config.cmake'
error:
error: Tried to build the target twice, with property sets having
error: these incompatible properties:
error:
error: - none
error: - none
error:
error: Please make sure to have consistent requirements for these
error: properties everywhere in your project, especially for install
error: targets.
I've done nothing but replace the source files for boost from 1.62 to 1.72.0. I couldn't find any relevant differences in the b2 documentation between those versions. Did I miss something?
I've tried removing the --with-atomic flag and it just fails on the next library with the same error. I've tried different options for --layout, threading, and architecture with no luck. Any suggestions on what I should investigate further to resolve this?

Answer 1

Apparently I've been doing it wrong this whole time. You shouldn't set --prefix and --stagedir to the same location. Previous iterations of boost don't seem to care about this issue. One of the later versions started caring which caused my problem.